The Godfather

Hagen is introduced as an unofficial but important part of the Corleone family. As a child he grew up in a broken family, the son of an abusivealcoholic. Hagen is saved by Sonny Corleone, who finds him on the street and takes him in to live with the Corleone family. Vito Corleone becomes a surrogate father to Hagen, but does not officially adopt him out of respect for the boy's father.

In the novel, Hagen offers to work for Vito after going through law school, knowing full well that he is not merely a successful olive oil importer, but the most powerful Mafia chief in the nation. Vito is more than willing to take Hagen into his employ, telling him that lawyers can steal more than a phalanx of gangsters. Hagen marries an Italian, Theresa, and has two sons, Frank and Andrew.

After longtime consigliereGenco Abbandando comes down with a terminal illness, Tom becomes acting consigliere, succeeding to the post formally after Genco's death. Vito is initially reluctant to give Tom the post full-time, considering that he is not Italian.